Satellites listened to the 2011 Japan quake and located fault beneath Spokane.

Last year, we reported on some mysterious booms in a small Wisconsin town that turned out to be small earthquakes. While it was an unusual story, it’s actually not that uncommon of an occurrence. Early in the summer of 2001, folks in Spokane, Washington started reporting similar booms. The sounds continued, off and on, for about five months. The mystery didn’t last long, as the earthquakes responsible were picked up by seismometers in the area. (A particularly loud one that took place exactly one month after the September 11, 2001 terrorist attacks in New York did rattle some nerves, however.)

In total, 105 earthquakes were detected, with a couple as large as magnitude 4.0. For most of them, there wasn’t good enough seismometer coverage to really pinpoint locations, but some temporary units deployed around the city in July located a number of events pretty precisely: the earthquakes were centered directly beneath the city itself.

While a dangerously large earthquake is pretty unlikely in Wisconsin, the possibility can’t be ignored in Washington. The 2011 earthquake in Christchurch, New Zealand was only a magnitude 6.3, but the damage was extensive because the epicenter was so close to the city. In L’Aquila, Italy, a swarm of small earthquakes in 2009 was followed by a deadly magnitude 6.3. (The poor public communication of risk during that swarm netted six seismologists manslaughter convictions.)

For obvious reasons, it’s important to learn more about what’s going on beneath Spokane. A group of researchers from the US Geological Survey and the Pacific Northwest Seismic Network have turned to satellites to start piecing the story together.

InSAR (or interferometric synthetic aperture radar) data from satellites allows scientists to detect exceedingly small changes in land surface elevation, such as occurs when crustal blocks shift during an earthquake. Data collected by European Space Agency and Canadian Space Agency satellites show surface movement along a fault running northeast from the center of the city. Despite the fact that the data were gathered from space, they were able to show a maximum change of about 15 millimeters.

The researchers used computer models to work out the earthquake characteristics that would be consistent with all the available data. They came up with shallow earthquakes centered 0.3 to 2 kilometers below the surface involving a thrust motion on the fault—meaning that one block is being pushed up and over the other—totaling about 45 millimeters.

Evidence of the fault in the landscape beyond city limits is inconclusive. The floodwaters from the draining of glacial Lake Missoula scoured that area, potentially erasing or obscuring any fault scars that had been present. There is a known fault that skirts the other side of the city, however, and it’s possible that this fault branches off it.

In order to assess the risk of larger earthquakes near Spokane, seismologists will have to learn more about the structure of the fault and what makes it tick. If you don’t understand the stress building along the fault, you can’t know how big the resulting earthquakes can be.

Your subwoofer does not impress me, mortal

The noise associated with these small quakes may have shaken up local residents, but the phenomenon isn't limited to small earthquakes. The 2011 magnitude 9.0 Tohoku-Oki earthquake in Japan also made some noise—enough that it was detectable from 270 kilometers up.

The European Space Agency’s GOCE satellite was not designed to be an earthquake eavesdropper. The satellite is basically a giant accelerometer capable of incredibly precise measurements of gravity, and it's normally used to study Earth processes like ocean circulation and melting ice sheets. But a group of researchers from France and the Netherlands decided to examine the satellite’s data for any signals related to the massive earthquake in Japan. They weren’t looking for changes of the Earth’s surface—they were looking for the direct effect of the earthquake’s infrasound boom reaching the satellite.

And that’s just what they found. The satellite’s accelerometer picked up the subtle effect of the acoustic wave traveling through it. What’s more, since the satellite’s orbit is still technically in the Earth’s atmosphere, it could detect the fluctuations in air density caused by the passing sound waves. The satellite's activity depend on maintaining it in an incredibly precise orbit by using jets to compensate for drag. The momentary increases in atmospheric density caused by the earthquake's sound waves increased the drag on the satellite, triggering the jets.

Since this had never been done before, the researchers claim the mantle of “first seismometer in orbit around the Earth” for the GOCE satellite. Apart from helping researchers interpret GOCE’s data, this “proof of concept” provides a new way to study interesting atmospheric phenomena related to earthquakes, like the disturbances in the ionosphere that can interfere with GPS systems.

While a dangerously large earthquake is pretty unlikely in Wisconsin, the possibility can’t be ignored in Washington.

You seem to be missing an explanation as to why it can't be ignored in Washington. Does it have to do with the fact that much of Eastern Washington is made of up Channeled Scablands so it's effectively sitting right on the bedrock?

While a dangerously large earthquake is pretty unlikely in Wisconsin, the possibility can’t be ignored in Washington.

You seem to be missing an explanation as to why it can't be ignored in Washington. Does it have to do with the fact that much of Eastern Washington is made of up Channeled Scablands so it's effectively sitting right on the bedrock?

No, more that there's legit tectonic activity out there. It's closer to plate boundaries, and there's more stuff going on in the crust.

While a dangerously large earthquake is pretty unlikely in Wisconsin, the possibility can’t be ignored in Washington.

You seem to be missing an explanation as to why it can't be ignored in Washington. Does it have to do with the fact that much of Eastern Washington is made of up Channeled Scablands so it's effectively sitting right on the bedrock?

As a Washington resident, it is clear to me why the possibility can't be ignored, but I see why it wouldn't be obvious to someone not from around here.

Basically, the west coast is sitting on a plate boundary, and the pacific plate is pushing into and under the north American plate. There's a lot of pressure here, and faults. We're known more for our rain than our earthquakes, but we deserve the recognition just as much as California. For more information, check out the ring of fire.

While a dangerously large earthquake is pretty unlikely in Wisconsin, the possibility can’t be ignored in Washington.

You seem to be missing an explanation as to why it can't be ignored in Washington. Does it have to do with the fact that much of Eastern Washington is made of up Channeled Scablands so it's effectively sitting right on the bedrock?

No, more that there's legit tectonic activity out there. It's closer to plate boundaries, and there's more stuff going on in the crust.

If you zoom in to the US map you need to be aware that the map is somehow culling the total number of quakes shown (around the edge of the viewport?). The default view only shows 4 quakes in WA and none in OR; but if you drag those two states to the center they're almost as densely covered as CA is. If you adjust the slider from 300-1000 quakes, CA appears to have about 2-3x as many quakes again.

That is amazing! I wonder what the projected lifespan is for the satellite, since it depends on correcting its orbit with jet/rocket bursts? Is it one that could be refueled, if we ever get another man-rated vehicle?

Despite the fact that the data were gathered from space, they were able to show a maximum change of about 15 millimeters.

And this:

Quote:

The satellite’s accelerometer picked up the subtle effect of the acoustic wave traveling through it. What’s more, since the satellite’s orbit is still technically in the Earth’s atmosphere, it could detect the fluctuations in air density caused by the passing sound waves.

Are absolutely amazing facts. I'm especially floored by the GOCE satellite and the fact that it can detect air pressure changes in the rarified environment of the atmosphere 270 km up. Any chances we could get more information on these satellites?

Yep quakes in WA, absolutely. This is how the great city of Seattle will end. Magnitude 8+. There are faults here running everywhere beneath us. We are just as vulnerable as California. It's just some sort of a coincidence that few major quakes occurred here since 1851 when first settlers came here. Not a lot of history. Natives have many oral stories of earth moving and ocean swelling. They were dismissed, until modern science found this:

Yep quakes in WA, absolutely. This is how the great city of Seattle will end. Magnitude 8+. There are faults here running everywhere beneath us. We are just as vulnerable as California. It's just some sort of a coincidence that few major quakes occurred here since 1851 when first settlers came here. Not a lot of history. Natives have many oral stories of earth moving and ocean swelling. They were dismissed, until modern science found this:

That is amazing! I wonder what the projected lifespan is for the satellite, since it depends on correcting its orbit with jet/rocket bursts? Is it one that could be refueled, if we ever get another man-rated vehicle?

While a dangerously large earthquake is pretty unlikely in Wisconsin, the possibility can’t be ignored in Washington.

You seem to be missing an explanation as to why it can't be ignored in Washington. Does it have to do with the fact that much of Eastern Washington is made of up Channeled Scablands so it's effectively sitting right on the bedrock?

But isn't the opposite true of earthquakes? My understanding is that it's much safer during an earthquake for a structure to be attached directly to bedrock than to have a large layer of soil, sand, dirt, or whatever between the structure and the bedrock.

A minor nit pick, but the Christchurch earth quake was close to the city only so far as it was at a very shallow depth. It could be right under a city but the depth of the quake and the geology of the area play a significant part in how destructive it can be. Christchurch was both shallow and had a geology such that the buildings were effectively sitting on a trampoline and that liquefaction was common. Destructiveness was also due to buildings having already been stressed in the first Greendale quake in September 2011.

On the sound part, you can hear the earthquakes and aftershocks coming if you are far enough away from it. In fact, after a few months, most staff were I worked could give a good estimate of the size and distance of an aftershock from the sound it made and how the building moved.

To be able to 'hear' these from orbit is pretty amazing!

(PS if you want to get a feel for how long the first quake lasted, try clapping your hands for 40 seconds)

But isn't the opposite true of earthquakes? My understanding is that it's much safer during an earthquake for a structure to be attached directly to bedrock than to have a large layer of soil, sand, dirt, or whatever between the structure and the bedrock.

Our house sits on bedrock being the Christchurch Port Hills and although it suffered damage, it was not like those in the areas where liquefaction occurred. Any aftershocks within about 3 kms from us and under the Port Hills hit with a bang with very little 'swaying' motion. Aftershocks that occur on the Canterbury Plains we can hear coming and result more in a rolling motion.

Since this had never been done before, the researchers claim the mantle of “first seismometer in orbit around the Earth” for the GOCE satellite.

I'm a little skeptical about "first". The NASA/JPL network of high precision GPS receiver ground stations around the world monitors, among other things, the shape of the ionosphere and troposphere as revealed by phase analysis of GPS satellite transmitters. The resulting data can mark things like underground nuclear tests and I'm presuming earthquakes as well.

Unless GOCE is doing all the processing on orbit. In that case, I guess the claim would stand.

Since this had never been done before, the researchers claim the mantle of “first seismometer in orbit around the Earth” for the GOCE satellite.

I'm a little skeptical about "first". The NASA/JPL network of high precision GPS receiver ground stations around the world monitors, among other things, the shape of the ionosphere and troposphere as revealed by phase analysis of GPS satellite transmitters. The resulting data can mark things like underground nuclear tests and I'm presuming earthquakes as well.

Unless GOCE is doing all the processing on orbit. In that case, I guess the claim would stand.

The idea is that things like electron perturbations in the ionosphere are indirect effects of the earthquake-caused acoustic waves, whereas this is the first instrument to directly measure them.

So, you know that neighbor that rolls down the street at 3 in the morning with all of his 1500 glorious watts doing their best to find the resonant frequency of your door frame? Turns out, solar-system wise, that's us.

I wonder what the projected lifespan is for the satellite, since it depends on correcting its orbit with jet/rocket bursts? Is it one that could be refueled, if we ever get another man-rated vehicle?

GOCE was launched in March 2009 and already has far surpassed its design lifetime. It has recently been brought into an even lower orbit. Even at this lower altitude, the remaining propellant might still last until near the end of 2013.

Sadly, the Canadians now have us by the throat as they know where our weaknesses lie. This Administration will oversee the rise of seismic terrorists on its watch.

Hey! Don't give these guys any ideas from this! Next thing you know, we'll have these guys using the seismic blame from job cuts to balancing out the budget..They would never blame themselves for their mistakes, NEVER!!